The structure of such inflator is relatively complex, however, so that it is the object of the invention to provide a good protection against excessive impact of heat for a vehicle occupant protection system by an inflator having a simpler configuration.
This is achieved with an inflator comprising a housing in which a combustion chamber including a pyrotechnic propellant for generating hot gas is arranged and which has at least one escape orifice toward the environment of the inflator. In the housing a coolant reservoir is arranged in which prior to activation of the inflator coolant is accommodated and which includes at least one coolant outlet orifice, wherein at least one of the at least one coolant outlet orifice is arranged in direct vicinity of at least one of the at least one escape orifice. This configuration ensures that especially in a first gas escaping phase immediately after activation of the inflator such a large portion of coolant is contained in the gas flow exiting from the escape orifice that the environment of the escape orifice is wetted and/or cooled. In this way, for instance, the protection of an inlet opening of an airbag can be achieved by wetting and/or cooling the fabric of the airbag. Also other areas of the environment of the escape orifice, for instance other sections of an airbag wall or sections of plugging material, foams or a seat lining, against which the hot gas exiting the escape orifice is flowing can thus be protected from heat impact by the cooling and/or wetting performed in the starting phase of the gas escape.
The coolant can escape at least partially in liquid form from the escape orifice of the housing of the inflator. This is possible due to the direct spatial vicinity of the coolant outlet orifice to the escape orifice in the housing of the inflator, as in this way the escaping hot gas causes the coolant to be entrained and atomized during escaping.
Preferably the coolant is non-combustible. For instance, water including additives lowering the freezing point such as CaCl2 can be used. What is important only is the fact that the coolant is liquid within a temperature range of from about −35 to +85° C., i.e. within the intended operating temperatures of an inflator in a vehicle.